Field
Embodiments disclosed herein relate generally to communication between a rotor and a stator, and, more particularly, to bi-directional communication between a rotor and a stator using a tangentially directed beam and a curved mirror arranged on the stator to direct the optical beam between the rotor and the stator.
Description of the Related Art
Many applications require the transmission of signals between a stationary structure (the stator) and a rotating structure (the rotor). Conventionally, slip rings are used for these applications. The slip ring allows for unlimited rotations of the rotor relative to the stator, in contrast to a flexible cable, which will fail after a finite number of rotations.
For example, one application is computed tomography (CT). CT scanners transmit data across a rotary interface. In order to enable such data transmission, slip rings are commonly employed. A slip ring is an electromechanical device that allows the transmission of power and electrical signals between the stator and the rotor. A slip ring can be used in any electromechanical system that requires rotation while transmitting power or signals.
A slip ring can include a stationary graphite or metal contact (brush) that rubs on the outside diameter of a rotating metal ring. As the metal ring turns, the electrical current or signal is conducted through the stationary brush to the metal ring, making the connection. Additional ring/brush assemblies can be stacked along the rotating axis to provide additional capability. Either the brushes or the rings are stationary and the other component rotates. Rotary transformers can be used as an alternative to slip rings in high-speed and/or low-friction applications. Some application use mercury-wetted slip rings, which are noted for their low resistance and stable connection. Mercury-wetted slip rings use a different principle and replace the sliding brush contact with a pool of liquid metal molecularly bonded to the contacts. During rotation, the liquid metal maintains the electrical connection between the stationary and rotating contacts. Disadvantageously, the toxicity of mercury can create safety risks. Accordingly, applications involving food manufacturing or processing, pharmaceutical equipment, or any other use where contamination could be a serious threat conventionally use precious metal contacts.
For applications using/generating high data rates such as CT scanners, the low data rates of electrical transmissions over slip rings make slip rings impractical. Optical rotary joints have been developed to support higher data transmission rates across rotary interfaces. Optical communication is capable of transmitting data at much higher rates than electrical communication techniques.
Conventional optical rotary joints generally include one or more light sources that emit optical signals predominantly radially between the stator and the rotor. These conventional optical rotary joints also use reflectors that have a conical shape (e.g., a hyperbolic or elliptical shape) to direct the radial light beams onto an optical receiver located at a focal point of the conical shape. The optical sources are conventionally spaced circumferentially about the rotor, and the reflectors and receivers are spaced circumferentially about the stator. Conventionally, the path of optical data transmission across the rotary joint (i.e., between the rotor and stator) is in a radial direction with respect to the rotor axis. Disadvantageously, these conventional optical rotary joints only transmit information in one direction, making many modern communication protocols (e.g., TCP/IP), and many error-correction techniques impractical for conventional optical rotary joints. Further, predominantly radial transmission of optical signals between the rotor and the stator results in an unfavorable trade-off between using a large number of optical sources/detectors and using large numerical aperture (NA) optical receivers/fibers.